1. Field of the Invention
This invention relates to a multiple component gas analyzer that analyzes various components contained in exhaust gas from vehicles.
2. Background Art
Conventionally, various gas analyzers are used in order to measure components in exhaust gas discharged from a vehicle such as an automobile. For example, as shown in Japan Patent laid open no. 11-230869, an infrared gas analyzer is used in order to measure the concentration of CO or CO2 and a chemiluminescence nitrogen oxide analyzer is used in order to measure the concentration of NOX. In addition, a hydrogen flame ionization analyzer to measure the concentration of THC (total hydro carbon) is also well-known.
With these analyzers, other components in the exhaust gas cause interference or quenching to the component as an object to be measured due to a system of these analyzers, thereby causing an error in the measurement result. As a result, for example, a detector for correcting interference or quenching is arranged separately inside of the infrared gas analyzer. In addition, in order to reduce quenching due to CO2 or H2O, the chemiluminescence nitrogen oxide analyzer diminishes the flow rate of the exhaust gas to take, dilutes the exhaust gas in advance or raises a degree of vacuum.
However, in case that interference is caused due to multiple components for the chemiluminescence nitrogen oxide analyzer, it is necessary to provide multiple detectors to correct interference for each component, resulting in complicated arrangement. In addition, if the flow rate of the exhaust gas is decreased or the exhaust gas is diluted for the chemiluminescence nitrogen oxide analyzer, the sensitivity or the precision is degraded, and the response of the measurement is also affected. If the degree of vacuum is raised, a large-size vacuum pump is necessary.
These problems such that the arrangement becomes complicated or large, or the measurement sensitivity, the measurement accuracy and the response of the measurement are degraded are a bottleneck for developing an exhaust gas analyzer that can be mounted on a vehicle and that can measure the exhaust gas continuously on a real time basis.
In addition, a conventional vehicle-mountable exhaust gas analyzer is provided with a heated piping or dehumidifier to remove moisture in order to prevent an adverse influence on the exhaust gas analyzer due to moisture (H2O) contained in the exhaust gas, however, the heated piping or dehumidifier consumes a lot of electric power. This becomes a bottleneck for making the exhaust gas analyzer vehicle-mountable.
More specifically, the conventional exhaust gas analyzer is so arranged that the sample gas is introduced into each analyzer through the introductory piping. Since CO, CO2, NOX, THC as being an object to be measured are mixed with H2O in the sample gas discharged from the above emission source, if the introductory piping is not heated, the moisture (H2O) in the sample gas condenses inside the introductory piping. If the condensation is caused, volume of the sample gas decreases and the concentration of the component as the object to be measured is calculated to be higher. As a result, the conventional exhaust gas analyzer uses a heated introductory piping provided with a heater as the introductory piping for the exhaust gas.
In addition, in case that the moisture is contained in the sample gas when measuring the concentration of CO and the concentration of CO2 by an NDIR analyzer, if CO is the component as the object to be measured, moisture contained in the sample gas causes moisture interference because an absorption wavelength region of the infrared light due to CO is close to an absorption wavelength region of the infrared light due to moisture (H2O), thereby to have an influence on the measurement value of CO analysis. Furthermore, if the moisture concentration in the sample gas is not stable, the influence of the moisture concentration also changes, which might cause an error in the measurement value of CO.
A CLD type NOX analyzer detects light of the ultraviolet region by a photo sensor and detects the concentration of NOX in a sample from a luminescence amount in a certain space to which the sample is introduced by making use of a nature that the luminescence amount varies in proportion to an amount of NOX molecule.
At this time, it is known that the luminescence amount decreases if moisture (H2O) or CO2 exists. This is a phenomenon called as quenching, and influences a measurement value of NOX. Furthermore, if the moisture concentration in the sample gas is not stable, the influence of the moisture concentration also changes, which might cause an error in the measurement value of NOX.
Then a conventional exhaust gas analyzer is provided with a dehumidifier in order to solve problems of the moisture interference for the NDIR analyzer, the quenching for the CLD type NOX analyzer and the unstable moisture concentration.
However, the heated piping or dehumidifier arranged for a conventional vehicle-mountable exhaust gas analyzer in order to solve the above-mentioned problems resulting from the moisture (H2O) contained in the exhaust gas consumes a lot of electric power. The power consumption consumed by the heated piping or the dehumidifier occupies greater part of the electric power consumed by the exhaust gas analyzer. (Japan Patent laid open no. 2002-5838.)
Conventionally, an exhaust gas analyzer to analyze component contained in exhaust gas discharged from a vehicle is generally of a type installed in an indoor laboratory. Then the exhaust gas has been analyzed during a driving experiment in the indoor laboratory. However, as a recent interest concerning an influence of the component contained in the exhaust gas on environment or human health has been growing, it is desired to analyze the exhaust gas discharged from the vehicle while the vehicle is actually driving on a road.
In order to make it possible to mount the exhaust gas analyzer on a vehicle, the exhaust gas analyzer has to be downsized, weight saved and electric power saved. However, since the conventional exhaust gas analyzer is provided with the heated piping or the dehumidifier whose electric consumption is big in order to exclude the adverse influence due to moisture existing in the exhaust gas, it is difficult to save the electric power.